The present invention relates generally to a crop harvester and more specifically to an attitude control system for a crop-gathering head having a pivotally connected pickup.
In the following specification and in the drawings, the crop harvester will be described and illustrated as a combine, but those skilled in the art will recognize the attitude control system of the present invention can be used with other implements.
When combining certain crops, it is desirable to maintain the pickup for the crop-gathering head a predetermined distance above the ground. For example, when a belt or conveyor type of pickup is used in the windrow pickup method of harvest, the height of the forward end of the pickup is regulated through gauge wheels located on either side of the unit. The pickup is pivotally connected about a generally horizontal transverse axis near the front of the crop-gathering head to allow the forward end to move up and down. The gauge wheels are adjusted just low enough to allow fingers located on the belt to gather in the grain, but high enough so that the fingers do not dig into the ground. The gauge wheels follow the ground contour raising and lowering the forward end of the pickup as necessary to maintain the predetermined distance. The angle between the pickup and the head changes as the gauge wheels follow the contour and/or as the head is raised and lowered.
The crop-gathering head includes an elongated harvesting platform. An auger rotates above the platform to draw the material conveyed by the pickup from the ground into a crop transferring opening. In this and similar type units, there is an optimum angle between the upper run of the pickup conveyor and the plane of the harvesting platform for most effectively feeding the material from the pickup to the auger. If the angle is increased beyond the optimum, the material is directed too far above the platform and above the centerline of the auger, which often results in bunching and slugging as the material travels in a loop before moving under the auger. In some cases the material is thrown over, rather than toward the lower front portion of the auger, causing backfeeding and possible jamming of the gathering head. If the angle between the platform and head is reduced too far below the optimum angle, the material is directed downwardly towards the platform and too far below the axis of the auger, breaking up the natural flow pattern from the pickup to the auger. The orientation of the stems or stalks is affected thus hampering effective flow through the auger. Bunching and slugging can occur with improper orientation of the pickup with respect to the crop-gathering head, particularly in long straw conditions.
To maintain the correct angle, the operator has to watch the pickup and the head, and when the angle increases or decreases from an optimum range, the head has to be lowered or raised, respectively, to cause the pickup to pivot on the head to maintain the desired angular relationship. An operator controlled hydraulic cylinder is activated to reposition the head and re-establish the angular relationship. Constant monitoring of the angle is fatiguing, especially where a harvester is being drawn by a tractor and the operator must turn around to view the machine. In areas where the ground is uneven or rolling, the angle between the pickup and head will continually deviate from the optimum range. In many instances, the operator simply fails to adjust the height of the head to maintain the proper attitude with respect to the pickup and bunching, slugging or backfeeding results.
In addition to directing the material to the auger properly, correct attitude of the pickup also assures that few rocks or other foreign material will be conveyed to the platform. In certain types of belt pickups, such as shown in U.S. Pat. No. 3,474,605, the conveyor has an upper run which is divided into a forward portion with a substantial inclination to prevent rocks and other foreign material from being picked up, and a rearward substantially horizontal portion so the crop is fed to the lower portion of the auger. In order to maintain the proper pickup pitch, the head height must be properly adjusted. If the head is too low, the inclination of the forward portion will be decreased, allowing more foreign material to enter the platform area. The rearward portion will be angled downwardly from the horizontal, directing the windrow below the optimum point on the auger. If the head is too high, the rearward portion of the pickup will be angled above the horizontal, impelling the windrow above the centerline of the auger and resulting in slugging or uneven feeding, as discussed above.